Skin provides an ideal delivery location for many drugs, including systemic drugs. Drug delivery through skin can be painless and provide sustained release, thereby increasing patient compliance. Systemic drugs delivered through skin do not undergo first pass metabolism, and skin delivery can allow systemic treatment with drugs, such as protein-based pharmaceuticals like antibodies and vaccines, that are otherwise susceptible to degradation or digestion in the gastrointestinal tract.
In addition, cosmetic ingredients for improving skin health or enhancing the appearance of skin must also be delivered across the skin's outermost layer, the stratum corneum. However, the delivery of both drugs and cosmetic ingredients across the stratum corneum is complicated by the skin's role as an efficient environmental barrier. The stratum corneum prevents many molecules, such as large molecules, protein drugs, and electrically-charged small molecules, from crossing its barrier.
Various methods have been explored for transporting drugs and cosmetics through the stratum corneum, including physical and chemical disruption of the stratum corneum. While chemical penetration enhancers have been used with varying success, they generally cannot transport large hydrophilic compounds, protein drugs, or electrically-charged small molecules across the stratum corneum and into systemic circulation. Instead, large hydrophilic compounds, protein drugs, and electrically-charged small molecules must often be delivered via routes having lower patient compliance, such as injection. Additionally, for molecules that can be transported with the use of chemical penetration enhancers, the chemical penetration enhancers can cause irritation. There remains a need for new penetration enhancing compositions that can provide transport of a wide variety of compounds across the stratum corneum to deeper layers of skin, or into systemic circulation.